Method and system for manufacturing frozen sushi that remains stable until consumption following thawing and refrigeration

ABSTRACT

The current document is directed to methods and systems for manufacturing frozen-sushi food products that remain texturally and compositionally stable while frozen and refrigerated for extended periods of time. A variety of different processing steps and ingredients are employed to prevent retrogradation of gelatinized starch in cooked sushi rice, including quick cooking of the rice, employing non-nutritive sweeteners in place of sugar, controlling the amount of salt in the sushi rice, and use of β amylase and gellan gum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.13/601,189, filed Aug. 31, 2012, which claims the benefit of ProvisionalApplication No. 61/529,713, filed Aug. 31, 2011.

TECHNICAL FIELD

The current document is directed to the manufacture of various types offrozen-sushi prepared foods that can be shipped and stored in freezingand sub-freezing conditions and then thawed and either immediatelyconsumed or refrigerated prior to consumption.

BACKGROUND

Modern sushi was initially created in Japan in the early 1800's. Thereare many different types of sushi made and consumed in Japan and otherAsian countries as well as types of sushi popular in the Americas andEurope. Cooked, vinegared rice is a common ingredient to all of thedifferent types of sushi. In Japanese sushi, the cooked vinegared riceis prepared from white, short-grain Japanese rice mixed with ricevinegar, sugar, and salt. It is generally cooled to room temperaturefollowing cooking and then combined with additional ingredients,including nori black seaweed wrappers, various types of seafood, varioustypes of vegetables, and other ingredients. While all of theseingredients contribute to the taste and texture of sushi, the taste andtexture of sushi rice is often a significant contributor or the maincontributor to the overall perception, to sushi consumers, of thequality and freshness of sushi products.

As sushi has become more and more popular around the world, and as thedemand for sushi has correspondingly increased, attempts have been madeto prepare frozen sushi products in order to achieve the samemass-production and mass-distribution efficiencies as obtained withother frozen, processed food products. Many of the ingredients in sushican be successfully frozen and subsequently thawed without significantlydegrading their taste and texture. However, until the development of theprocesses and systems to which the current document is directed, therehas been no satisfactory method for freezing sushi rice. The taste andtexture of rice significantly degrades while the rice is frozen andrefrigerated, rendering thawed, thawed and refrigerated, and heatedfrozen sushi unsatisfactory to sushi consumers. The degradation of sushirice is particularly prevalent in commercial environments, in whichfrozen-storage and refrigeration units often fail to maintain constanttemperatures, leading to fluctuating temperatures, fluctuating humidity,and even to multiple unintended freeze/thaw cycles.

SUMMARY

The current document is directed to methods and systems formanufacturing frozen-sushi food products that remain texturally andcompositionally stable while frozen and refrigerated for extendedperiods of time. A variety of different processing steps and ingredientsare employed to prevent retrogradation of gelatinized starch in cookedsushi rice, including quick cooking of the rice, employing non-nutritivesweeteners in place of sugar, controlling the amount of salt in thesushi rice, and use of amylase and gellan gum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a sushi food product, prepared by the currentlydisclosed methods and systems, that is stable when frozen andrefrigerated, allowing the frozen sushi food product to be mass producedin a commercial facility, frozen, and distributed as a frozen sushi foodproduct over large geographical areas, and stored in freezing andrefrigeration conditions for significant periods of time prior tothawing and use.

FIGS. 2-3 illustrate two biopolymers, amylose and amylopectin, thattogether occur in starch.

FIG. 4 illustrates retrogradation of starch.

FIG. 5 illustrates the chemical structure of the gellan-gum biopolymer.

FIG. 6 illustrates the chemical structure of the artificial,non-nutritive sweetener sucralose.

FIGS. 7-16 illustrate the manufacture of a frozen-sushi food productusing the methods and systems to which the current document is directed.

DETAILED DESCRIPTION

As discussed above, sushi is a popular food product that was originallydeveloped in southeast Asia as a fermented food product. Modern,non-fermented sushi was developed in the early 1800's in Japan as anearly form of convenience food that can be quickly prepared and eaten byhand. The traditional sushi ingredients, including vinegar, providepreservative-like characteristics that allow sushi to remain stable atroom temperatures for significantly longer periods of time thannon-preserved, processed foods. However, when sushi is frozen, thesesame ingredients turn out to promote retrogradation of the gelatinizedstarch produced by cooking sushi rice, leading to loss of hydration,staleness, unpleasant textures, and unpleasant odors.

Prior to research and development efforts that were undertaken to createthe currently disclosed methods and systems for preparing stable frozensushi, previous attempts to manufacture frozen-sushi products werecommercial failures. Although many different approaches have been triedto created sushi products that can be frozen for shipment and storage,the failure to recognize that traditional sushi ingredients, whilehaving preservative characteristics at room temperature, promoteretrogradation of gelatinized starch at freezing temperatures resultedin sushi products susceptible to retrogradation. In addition, improperconcentrations of salt in sushi food products may promote deteriorationof the products even at refrigeration temperatures. For example,attempts have been made to replace sucrose with other types ofcarbohydrate sweeteners, including trehalose. However, like the sucrosefor which trehalose has been substituted, trehalose and othercarbohydrate sweeteners promote retrogradation of gelatinized starch inthe same fashion as retrogradation is promoted by sucrose at freezingand below freezing temperatures. Salt, by contrast, when used at anappropriate concentration, inhibits retrogradation of gelatinizedstarches at refrigeration temperatures of between 32° Fahrenheit and 40°Fahrenheit. However, at higher concentrations, salt may induce anunpleasant, gummy texture in sushi rice. Until the research anddevelopment efforts that produced the currently disclosed process werecarried out, it was not known that carbohydrate sweeteners promoteretrogradation of sushi rice at freezing and below-freezing temperaturesand it was not known that a proper concentration of salt inhibitsretrogradation of gelatinized starches at refrigeration temperatures ofbetween 32° Fahrenheit and 40° Fahrenheit.

FIG. 1 illustrates a sushi food product, prepared by the currentlydisclosed methods and systems, that is stable when frozen andrefrigerated, allowing the frozen sushi food product to be mass producedin a commercial facility, frozen, and distributed as a frozen sushi foodproduct over large geographical areas, and stored in freezing andrefrigeration conditions for significant periods of time prior tothawing and use. The sushi roll 102 is an example of uramaki sushi andis commonly referred to as a “California roll.” The California roll hasthe shape of a cylindrical section with a diameter that typically rangesfrom 1.5 to 2.5 inches and a height that typically ranges from between 1and 2 inches. When manufactured by the currently disclosed process, thedimensions are controlled to relatively precise tolerances to produceuniformly dimensioned California rolls having desired dimensions.

The California roll 102 includes an outermost, cylindrical coating ofsesame seeds, such as sesame seed 104. This outer coating of sesameseeds coats the curved, vertical surface of a cylindrical of sushi rice.The cylindrical layer of sushi rice 106 overlies an inner, thincylindrical layer 108 of nori or another type of processed seaweed. Aninner solid cylindrical portion of the California roll 110 includesavocado and real or imitation crab, and may additionally includeseasonings, mayonnaise, and other ingredients.

FIGS. 2-3 illustrate two biopolymers, amylose and amylopectin, thattogether occur in starch. As shown in FIG. 2, the basic chemical unit ofboth the amylose and amylopectin biopolymers is D-glucose 202. Glucoseis a commonly occurring natural monosaccharide. Glucose contains sixcarbon atoms sequentially numbered 1-6 in FIG. 2. The first carbon atom204 is part of an aldehyde functional group and the remaining fivecarbon atoms 206 are bonded to hydroxyl groups. While D-glucose mayoccur in the open form 202 in solution, it most commonly inhabits aring-like structure 206 in which the oxygen atom of the hydroxyl groupassociated with the fifth carbon covalently binds to the first carbonatom 204 to form a hemiacetal, as indicated by the dashed arrow 208 inFIG. 2. The D-glucose molecule is an example of a chiral molecule inwhich the spatial arrangements of the functional groups as well as thecovalent bonding between atoms determines the identity of themonosaccharide. Interchanging the positions of the hydrogen and hydroxylsubstituents at one or more of the carbon atoms 2-6 leads to differentmonosaccharides, including D-allose, D-altrose, D-mannose, D-galactose,and other such different monosaccharides. Formation of the cyclic formof the molecule introduces an additional chiral center at the firstcarbon atom. When the hydroxyl group is pointed downward, as in thecycle structure 206, the cyclic monosaccharide is referred to as“α-D-glucopyranose.” When the hydroxyl group points outward or, in otherwords, when the hydrogen and hydroxyl group positions are interchanged,the molecule is referred to as “β-D-glucopyranose.” Two glucopyranosemolecules 206 and 210 can be chemically combined, through a condensationreaction, to produce a variety of different disaccharide molecules,including the disaccharide maltose 212 shown in FIG. 2. In maltose, thefourth carbon atom 214 of one α-D-glucopyranose subunit is attached tothe first carbon atom 216 of a second α-D-glucopyranose subunit throughan oxygen-atom bridge 218, referred to a s glycosidic linkage.” As shownin FIG. 3, the biopolymer amylose 302 is composed of a large number ofα-D-glucopyranose subunits linked together as they are linked togetherin maltose (212 in FIG. 2). The biopolymer amylopectin 304 includesamylose-like chains of α-D-glucopyranose subunits but additionallyincludes branches in which an α-D-glucopyranose subunit, such asα-D-glucopyranose subunit 306, is additionally linked through anoxygen-atom bridge 308 from the sixth carbon 310 to the first carbon 312of a different α-D-glucopyranose subunit. In FIG. 3, the arrows 316-320indicate a continuation of the amylose chain to additional subunits.Amylose biopolymers often include from between 300 and 3000α-D-glucopyranose subunits while amylopectin often contains between 2000and 200,000 α-D-glucopyranose subunits. Amylopectin generally includesbranch points at every 24 to 30 α-D-glucopyranose subunits and istherefore a highly branched, tree-like biopolymer. Both amylose andamylopectin biopolymers can inhabit various different types oflarge-scale, secondary structures, including disordered forms as well ashelical structures.

Starch is generally composed of both amylose and amylopectinbiopolymers. A typical ratio, by weight, is 70 percent amylopectin and30 percent amylose, but the ratio may differ significantly in differenttypes of plant materials, including rice. Low-amylose rice, for example,may contain 10%, 5%, or less amylose, by weight. Amylopectin has asignificantly lower tendency to undergo retrogradation during storagethan amylose, as a result of which use of low-amylose rice has beenidentified, during the research efforts that led to the currentlydisclosed methods and systems, as contributing to production of stablefrozen sushi food products.

FIG. 4 illustrates retrogradation of starch. As shown in FIG. 4, in atypical plant product, such as a rice grain, the amylose and amylopectinbiopolymers that together compose starch are in semi-crystalline state402 in which the biopolymers have well-ordered, double-helical secondarystructures that are arranged in parallel, higher-order supermolecularlattices. Plants and animals use starch to store carbohydrate in a formthat does not increase internal osmolarity of plant and animal cells, aswould be the case where monosaccharides concentrated within cells as anenergy reserve. When carbohydrate energy sources are needed, enzymes,such as the enzyme β amylase, remove disaccharide maltose subunits fromthe reducing, or hemiacetal, end of amylose and amylopectin biopolymers.

When starch-containing food products are cooked, the amylose andamylopectin biopolymers become disordered and hydrated 404. Thecrystalline, well-ordered biopolymers 402 become gelatinized or, inother words, disordered and hydrated to form a highly viscous solution404. However, when the gelatinized starch is cooled, left at roomtemperature for long periods of time, or frozen, the amylose andamylopectin biopolymers begin to assume a more well-ordered,semi-crystalline state 406 that is the product of the retrogradationprocess. As the biopolymers re-associate into well-ordered structures,water is expelled from the biopolymers. Retrogradation leads tostaleness and a marked change in the texture, taste, and odor of acooked-starch-containing preparation. Research efforts employed duringdevelopment of the currently disclosed methods and systems has revealedthat the retrogradation process is significantly promoted, atnear-freezing, freezing, and sub-freezing temperatures, by the presenceof monosaccharide, disaccharide, and polysaccharide sweeteners, such assucrose, fructose, and trehalose. In addition, suboptimal concentrationsof salts, including table salt NaCl, promote retrogradation atrefrigeration temperatures of between freezing and 40° Fahrenheit. It isthe retrogradation process, discussed above with reference to FIG. 4,that leads to the significant deterioration in frozen sushi productsduring storage and refrigeration, particularly when temperaturesfluctuate, as they often do in commercial frozen-storage andrefrigeration environments.

FIG. 5 illustrates the chemical structure of the gellan-gum biopolymer.Gellan gum is a water-soluble biopolymer that is used as a gelling agentin a variety of different food products. It is a substitute for agar andis a much more effective gelling agent, by weight, than agar. Thegellan-gum biopolymer 502 is a repeating sequence of a tetrasacchariderepeating unit 504 that includes β-D-glucopyranose,β-D-glucuronopyranose, β-D-glucopyranose, and α-L-rhamnopyranose. Thefour pyranoses within the repeating unit are linked together by β1-4glycosidic linkages and the repeating units are linked together by α1-3glycosidic linkages. Gellan gum comes in two commercial forms: (1)high-acyl gellan gum, which is the native biopolymer; and (2) low-acylgellan gum, which is prepared by de-esterification of native gellan gum.The native gellan-gum polymer features acetyl and glyceryl esters ofcertain of the hydroxyl groups of the pyranose subunits. The acetyl andglyceryl esters may be converted into free hydroxyl groups by any ofvarious processes.

FIG. 6 illustrates the chemical structure of the artificial,non-nutritive sweetener sucralose. Sucralose 602 is between 300 and 1000times sweeter than sucrose, twice as sweet as saccharine, and threetimes as sweet as aspartame. It is stable over a wide range oftemperature and pH conditions. Sucralose is one example of anon-nutritive sweetener that can be used, in place of sugar or othercarbohydrate-based sweeteners, in the preparation and processing of ricefor frozen sushi products in order to prevent or inhibit retrogradationof the sushi rice during frozen storage and refrigeration.

FIGS. 7-16 illustrate the manufacture of a frozen-sushi food productusing the methods and systems to which the current document is directed.First, low-amylose, sweet rice is soaked for two or more hours incooking solution. The cooking solution is prepared by combining waterand low-acyl gellan gum in the ratio 8.5 lbs. of water and 20 g oflow-acyl gellan gum. Variations in this ratio are possible, including 15g-25 g of low-acyl gellan gum to 8.5 lbs. of water, 10 g-30 g oflow-acyl gellan gum to 8.5 lbs. of water, 10 g-50 g of low-acyl gellangum to 8.5 lbs. of water. The low-acyl gellan gum complexes with lowamylose rice to provide a pleasant, non-sticky texture and body to thecooked rice. Soaking the rice prepares the rice kernels for fastcooking, and fast cooking is a significant contributor to thepreparation of stable frozen-sushi food products.

Next, the soaked rice is cooked. FIG. 7 illustrates the rice-cookingsubsystem employed in one commercial implementation of the frozen-sushimanufacturing process. The rice is cooked in a series of large pressurecookers 702-704. Each pressure cooker is heated by a natural-gas heatingunit that emits greater than 200,000 British Thermal Units (“BTUs”) perhour. In FIG. 7, the natural-gas heating units reside below and withinmetal heating stands 705-707. The solution for cooking is preheatedwithin the pressure-cooker pots to boiling. It is important that thecooking solution is preheated in order to reduce cooking times. Inaddition, the soaked rice is placed in stainless-steel mesh-like vesselsthat are lowered into the pressure-cooked pots so that the rice does notcome into contact with the sides of the pressure-cooker pots. Isolationof the rice from the pressure-cooker-pot surfaces ensures that the riceis uniformly heated, during the cooking process, and that an externallayer of rice is not burnt, caramelized, or otherwise deleteriouslyaffected by the high heat present on the pressure-cooker pot surfaces.The pressure cookers are sealed and the rice is cooked for seven minutesat 15 pounds per square inch (“psi”). The cooking times and pressuresmay vary with pressure-cooker volumes, heat sources, and other suchparameters. In one alternative implementation, the cooking times mayvary from 6 to 8 minutes and the pressure may vary from 10 psi to 20psi. Following cooking, the pressure cooker is removed from the heatsource and allowed to stand for ten minutes. The standing time may vary,in additional implementations, from 8-12 minutes, from 7-14 minutes,from 6-15 minutes, and for longer time periods. In additionalimplementations, commercial rice cookers may be used in place ofpressure cookers.

A next step involves addition of a vinegar solution to the cooked rice.The vinegar solution is prepared by combining five percent whitedistilled vinegar, salt, water, sucralose, and high-acyl gellan gum inthe ratios:

570 g of 5% white distilled vinegar;

90 g salt;

1040 g water;

0.7 g sucralose; and

20 g high-acyl gellan gum.

These ratios may vary with different implementations. The vinegarcontent may, for example, vary from 560 g to 580 g, from 550 g to 590 g,and from 530 g to 610 g. The salt content may vary from 85 g to 95 g.The sucralose content may vary from 0.5 g to 0.8 g or from 0.4 g to 1.0g, and the high-acyl-gellan-gum concentration may vary from 15 g to 25 gor from 10 g to 30 g, in alternative implementations. As discussedabove, the sucralose is a non-nutritive sweetener that replaces sucrose,which is commonly used in sushi rice, and which replaces the variousmonosaccharide, disaccharide, and polysaccharide sucrose substitutesthat have been tried in various commercial sushi products. The amount ofsalt added to the vinegar solution is calculated to form a weakassociation with amylopectin that, in turn, facilitates an associationwith the gellan gum that prevents strong amylopectin/salt complexes thatrender cooked rice gummy and unpleasant. The high-acyl gellan gumprovides a pleasant, elastic texture to the cooked rice and renders thecooked rice more durable with respect to mechanical processing.

An additional enzyme solution is used in the second step. The enzymesolution is prepared by combining water with the enzyme β amylase in theratio:

1100 g water; and

7.5 g β amylase.

The β amylase inhibits retrogradation at refrigeration temperatures andalso cleaves the amylopectin biopolymer to weaken amylopectin gellationand reduce the gummy texture of the cooked rice. In alternativeimplementations, the amount of β amylase may vary from 7.0 g to 8.0 g,6.5 g to 8.5 g, or from 6.0 g to 9.0 g.

FIG. 8 illustrates a drum containing prepared vinegar solution. Theabove-described vinegar solution is hand-pumped using a pump handle 802from the vinegar-solution-containing drum 804. After the cooked rice hasstood for ten minutes in the pressure cooker, the pressure is relievedand the pressure-cooker lid is removed from the pressure-cooker pot.Vinegar solution is combined with the cooked rice until the vinegarsolution is evenly distributed among the rice grains and the ricetemperature has cooled to 160° F. In alternative implementations, thetemperature may vary from 155-165° F., 150-170° F., 130-170° F., or120-180° F. At this point, enzyme solution is added to the rice andmixed into the rice until the rice is evenly distributed. Theabove-described ratios for the ingredients of the vinegar solution andenzyme solution describe the amount of vinegar solution and enzymesolution used for each ten pounds of uncooked, low amylose sweet rice.

FIG. 9 illustrates a mixing subsystem used in one commercialimplementation of the frozen-sushi manufacturing process to evenly mixthe vinegar and enzyme solutions within the cooked rice. The rice,vinegar solution, and enzyme solution are loaded into a rotating drum902 that is spun at a speed and for a time selected via an operationconsole 904.

FIG. 10 shows the loading assembly of an initial processing subsystemfor preparing frozen sushi. Once the rice, vinegar solution, and enzymesolution have been thoroughly mixed, the rice is loaded into largerectangular pans. The rectangular pans 1002 and 1004, including cookedrice, are loaded onto a vertical conveyor that raises the rectangularpans up and over to pour the cooked rice into a hopper 1006 at the topof the loading assembly of the initial processing subsystem.

FIG. 11 illustrates the first processing subsystem in a side view. Asdiscussed above with reference to FIG. 10, the rice is raised and dumpedinto a hopper 1006 at the top of the processing subsystem. A long,pliable conveyor belt 1102 extends from a roller 1104 in the lowerportion of the processing subsystem outward to additional downstreamprocessing subsystems. Sesame seeds are contained in a second hopper1106 and are evenly distributed across the pliable conveyor belt as theconveyor belt moves from the roller 1104 underneath the hopper 1106containing the sesame seeds. Rice from hopper 1006 is spread onto one ormore upper, short conveyor belts 1108 and 1110 and evenly layered overthe sesame seeds on the long, pliable conveyor belt 1102. Nori seaweedwrap 1112 is layered on top of the rice layer, distributed from a largerotating roll 1114 of nori seaweed wrap. Thus, the long pliableconveyor, as it exits from the first processing subsystem 1116, containsa bottom layer of sesame seeds, an intermediate layer of cooked rice,and a top layer of nori seaweed wrap.

FIG. 12 shows a next step in manufacture of the frozen-sushi product. Asshown in FIG. 12, a processing employee 1202 places peeled and sectionedavocado 1204 and, in certain implementations, any other vegetable, fish,or shell-fish ingredients, onto the top of the nori-seaweed-wrap layermoving along the long, pliable conveyor belt. A next processingsubsystem 1206 includes a hopper 1208 filled with imitation-crabmixture. The imitation-crab mixture is forced under pressure through adispensing tube 1210.

FIG. 13 illustrates application of the imitation-crab mixture to theavocado/nori-seaweed-wrap layer of the nascent, continuous, multi-layerfrozen sushi traveling along the extended pliable conveyor belt. Theimitation crab is forced through the dispensing tube 1210 and adispensing tub nozzle 1212 to form a continuous roughly cylindricallayer 1214 of imitation-crab mixture above the avocado/nori-seaweed-wraplayer as the pliable conveyor belt continues to move forward in theindicated direction 1216.

FIG. 14 shows a third processing subsystem. The third processingsubsystem includes a series of mechanical rollers, such as mechanicalroller 1302, that forces the pliable conveyor belt from a flat shapeinto a rolled, cylindrical shape 1304, thus rolling the flat layers ofsesame seed, cooked rice, nori-seaweed-wrap, avocado, and imitation-crabmixture into a long, continuous sushi roll.

FIG. 15 illustrates a fourth processing subsystem. The long, continuoussushi roll emanating from the mechanical rollers 1502 enters a choppingsubsystem 1504 that mechanically chops the long, continuous sushi rollinto sushi-roll sections 1506 that are loaded into a rotating drum 1508and mechanically chopped by a parallel chopping subunit 1510 into thefinal sushi rolls, illustrated in FIG. 1, which are lowered onto asecond long, continuous conveyor belt 1512. FIG. 16 illustrates thefourth processing subsystem and second continuous conveyor belt from adifferent perspective. As shown in FIG. 16, the chopped, final sushiproduct 1602 travels along the second conveyor belt to a pickup station1604 where the sushi rolls are placed onto trays 1606. The trays ofsushi rolls are then loaded onto racks and placed into a flash-freezingenvironment. The frozen sushi can then be packaged for distribution anddelivery.

The process illustrated in FIGS. 7-16 can be varied to produce manydifferent types of frozen-sushi food products. Different types ofvegetables and seafood can be layered about the nori seaweed wrap toproduce different types of California rolls. In addition, ordering ofthe application of various substances to the long continuous conveyorbelt may be altered to produce various different types of sushi, as, forexample, sushi products in which the seaweed wrapper forms the outermostlayer.

Although the present invention has been described in terms of particularembodiments, it is not intended that the invention be limited to theseembodiments. Modifications within the spirit of the invention will beapparent to those skilled in the art. For example, as discussed above,the above-described process can be altered in order to produce manydifferent types of frozen-sushi products. Various different types ofnon-nutritive sweeteners can be used in place of sucralose and variousdifferent types of gel-promoting substances may be employed in additionto, or instead of, gellan gum. Many different types of ingredients canbe combined to produce the various different types of frozen sushi.However, to prevent deterioration of the sushi product during freezing,frozen storage, and subsequent refrigeration, carbohydrate-basedsweeteners need to be avoided and the salt concentration needs to becarefully controlled, as discussed above.

It is appreciated that the previous description of the disclosedembodiments is provided to enable any person skilled in the art to makeor use the present disclosure. Various modifications to theseembodiments will be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to otherembodiments without departing from the spirit or scope of thedisclosure. Thus, the present disclosure is not intended to be limitedto the embodiments shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

The invention claimed is:
 1. A process that produces frozen sushi foodproducts that are stable when stored at sub-freezing, freezing, andabove-freezing refrigeration temperatures, the process comprising:cooking low-amylose, sweet rice; combining the cooked rice with a firstprocessing solution that includes water, vinegar, salt, a non-nutritivesweetener, and low-acyl gellan gum by adding the first processingsolution and cooked rice to an electro-mechanical tumbling subsystemthat mixes the first processing solution into the cooked rice; afteraddition of the first processing solution to the cooked rice, waitingfor the cooked rice to cool to between 130° F. and 160° F., and adding asecond processing solution to the mixture of the cooked rice and firstprocessing solution, the second processing solution comprising water andlow-acyl gellan gum; layering the cooked rice with one or moreadditional food-product layers to form a continuous multi-layerednascent product; rolling the multi-layered nascent product into acylindrical, continuous sushi roll; cutting the continuous sushi rollinto individual sushi rolls; and freezing the individual sushi rolls;wherein the first processing solution is prepared by combining 570 gramsof 5% white distilled vinegar, 90 grams of sodium chloride, 1040 gramsof water, 0.7 grams of sucralose, and 20 grams of high-acyl gellan gumfor addition to a quantity of cooked low-amylose sweet rice that weighed10 lbs. prior to cooking.
 2. A method for preparing sushi rice that isstable when frozen and/or refrigerated, the method comprising: soakinglow-amylose, sweet rice for two hours or more in water; pressure-cookingthe soaked low-amylose, sweet rice for between 6 and 8 minutes atbetween 10 and 20 psi; and combining the cooked rice with a firstprocessing solution that includes water, vinegar, salt, a non-nutritivesweetener, and low-acyl gellan gum; after addition of the firstprocessing solution to the cooked rice, waiting for the cooked rice tocool to between 130° F. and 160° F., and adding a second processingsolution to the mixture of the cooked rice and first processingsolution, the second processing solution comprising water and low-acylgellan gum; wherein the first processing solution is prepared bycombining 570 grams of 5% white distilled vinegar, 90 grams of sodiumchloride, 1040 grams of water, 0.7 grams of sucralose, and 20 grams ofhigh-acyl gellan gum for addition to a quantity of cooked low-amylosesweet rice that weighed 10 lbs. prior to cooking.